Studies of hypervalent iron in aqueous solutions. 1. Radiation-induced reduction of iron(VI) to iron(V) by CO2-

Iron(VI) can be reduced in aqueous solutions to iron(V) by pulse radiolytically generated CO/sub 2//sup -/, k/sub 3/ = (3.5 +/- 0.1) x 10/sup 8/ M/sup -1/ s/sup -1/. The respective UV and visible spectra for these hypervalent oxidation states or iron are reported. It was found that formate reacts 10/sup 5/ times faster with Fe(V) than with Fe(VI). Other kinetic rate measurements include the following: k/sub 4/(O/sub 2//sup -/ + Fe(VI)) = (5.71 +/- 0.17) x 10/sup 3/, k(NADA + Fe(VI)) = 77.1 +/- 4.4, k(HCOONa + Fe(VI)) = (2.33 +/- 0.4) x 10/sup -2/, k(EtOH + Fe(VI)) = (1.47 +/- 0.7) x 10/sup -3/, k(DPTA + Fe(VI)) = (8.53 +/- 0.32) x 10/sup -4/, k(HCOONa + Fe(V)) = (2.48 +/- 0.32) x 10/sup 3/ M/sup -1/ s/sup -1/. The results are discussed in terms of their possible role in Fe(VI) oxidation processes.